1. Field of Invention
This invention relates generally to the field of weaklink devices and, more particularly, to weaklink devices including electrokinetic pumps, and to electrokinetic pumps suitable modified for use as weaklinks as well as for other purposes.
2. Description of the Prior Art
There are many examples in commercial and military applications of the transmission or management of large amounts of energy under the control of safety-critical systems. These control systems must maintain the energy release within the safe bounds established for the process, as well as insure against abnormal (and possibly catastrophic) release of large amounts of energy due to system malfunction, whether accidental, malevolent or due to normal but uncorrected wear and tear.
Properly designed control systems typically include one or more “weaklinks.” A “weaklink” element in a control system is taken herein to mean an element, critical to control system function, whose activation or failure will cause the system to become safe before serious negative consequences result. As noted by Covan and Cooper, weaklinks are advantageously designed to respond passively, relying on predictable physical or chemical properties to insure system safety (Covan, J. M., and Cooper, J. A., “Predictable Safety in the Control of High Consequence Systems,” Third IEEE International High-Assurance Systems Engineering Symposium, Nov. 13-14, 1998, Washington, D.C.). Weaklinks have also found application in off-shore equipment and components, such as undersea tubes or pipes, at risk for unforeseen pulling forces due to ships' anchors or fishing gear (U.S. Pat. No. 5,924,741).
Microfluidics is a research and engineering discipline dealing with transport phenomena and fluid-based devices at microscopic length scales. Some authors state that microfluidic devices have the potential to effect a major change in instrumentation by producing cheap, disposable systems for the mass market. See, for example “Fundamentals and Applications of Microfluidics,” by N.-T Nguyen and S. T. Wereley, Artech House, 2002. Therefore, a need exists in the art for weaklink devices based upon microfluidics, offering the possibility of employing multiple microfluidic weaklink devices in safety systems with multiple levels of redundancy, thereby increasing the overall reliability of the safety systems.